Optical bypass switch

ABSTRACT

An optical bypass switch includes a normal state and a bypass state, a transmission optical fiber having a signal withdrawn therefrom and injected thereto in its normal state so as to be capable of use in a ring or bus architecture. In the bypass state of the switch, the transmission optical fiber is substantially disengaged so that a signal being transmitted thereby can bypass the switch, and in this state optical fibers connected to a transmitter and a receiver of the bypass switch are maintained in a bent attitude so as to allow signals to be withdrawn and injected thereinto. A loop back path, e.g. a connector optical fiber, is provided which allows a path between the transmitter and the receiver to be completed in the bypass state of the bypass switch, and logic circuitry is provided for analyzing signals detected by the receiver which should have originated from the transmitter for evaluating a state of operation of the transmitter, receiver, and connecting means therefor. Whenever the logic circuitry detects a malfunction in any of these elements, e.g. the transmitter, the receiver and connecting structure therefor, the optical bypass switch is kept in its bypass state and prevented from re-engaging the transmission fiber so as to prevent the bypass switch from optically coupling to the transmission fiber when its electro-optic elements are not functioning properly.

BACKGROUND OF THE INVENTION

The present invention relates to an optical bypass switch for a ring orbus network, and to preferred drive mechanisms therefor, and preferredconstructions for bending optical fibers within the switch for couplinglight between electro-optic transducers and cores of optical fibers.

Beals et al., U.S. Pat. No. 4,822,125, the disclosure of which isincorporated herein by reference, describes an optical fiber coupler foruse in a ring or bus architecture whereby a transmission optical fiberis bent so as to remove a signal therefrom, and also bent so as toinject an optical signal therein, the coupler including attenuatingmeans between the injection and withdrawal locations for attenuating anysignal left within the optical fiber so as to improve signal-to-noiseratios between any non-removed portion of the signal in the fiber andthat being injected. Though this coupler advantageously allows couplingto the transmission optical fiber in normal use, a need exists for acoupler which is capable of evaluating its state of operation in itsbypass state and utilizing this information so as to minimize chancesthat the coupler will be returned to its normal state whenopto-electronic or interconnecting components thereof are notfunctioning properly.

SUMMARY OF THE INVENTION WITH OBJECTS

It is an object of the invention to eliminate the above noted drawbackand to provide an optical bypass switch which includes means forevaluating a state of a transmitter and receiver as well asinterconnecting components therefor and determining if these elementsare functioning properly prior to returning the coupler to its normalstate.

These and other objects of the invention are achieved by an opticalbypass switch, comprising:

an optical receiver;

an optical transmitter;

means for withdrawing a first optical signal from a first bend in atransmission optical fiber at a first location and transmitting thefirst optical signal to the receiver;

means for injecting a second optical signal from the transmitter intothe transmission optical fiber at a second bend at a second locationdownstream of the first location on the transmission optical fiber;

bypass means for disengaging the withdrawing means and the injectingmeans from the transmission fiber in a bypass state so that the firstoptical signal can be transmitted past the withdrawing and injectingmeans, the bypass means including connector means for connecting thetransmitter with the receiver so that signals transmitted by thetransmitter can be detected by the receiver in the bypass state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a first preferred embodiment of the invention, acoupler shown therein being illustrated in its normal state;

FIG. 2 illustrates the coupler of FIG. 1 in its bypass state;

FIG. 3 illustrates detailed structure of a bypass drive mechanismuseable in the embodiment of FIGS. 1 and 2;

FIG. 4 illustrates the bypass drive of FIG. 3 in its bypass state; and

FIG. 5 illustrates a detailed construction of a bending mechanism forbending a transmission optical fiber in an optical bypass switch asillustrated in FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 illustrate plan views of a first embodiment of an opticalbypass switch according to the invention, FIG. 1 illustrating the bypassswitch in its normal state when normal coupling and communication with atransmission optical fiber 2 is achieved, and FIG. 2 showing a bypassstate where the transmission optical fiber is decoupled and means areengaged for connecting a path between a transmitter 5 and a receiver 6.

Referring to these figures, the optical bypass switch is optimallyusable in either a bus or ring network which utilizes a transmissionoptical fiber 2 and any desired protocol. The transmission optical fiber2, in a normal state of the optical bypass switch 1, is bent betweenfirst and second members 11, 13 about a radius sufficiently small suchthat light can be withdrawn from a core of an optical fiber through aside surface thereof and injected into a receiver optical fiber 4,optimally using a focusing lens 21. The lens can be an in-plane lens oran out-of-plane lens, a preferred out-of-plane lens being disclosed inUken, U.S. Pat. No. 4,741,585, the disclosure of which is incorporatedherein by reference. Light is withdrawn from the transmission fiber 2,focused by the lens 21, transmitted by the fiber 4, and detected by thereceiver 6. In addition, a further bend created in the transmissionfiber 2 by the members 11, 13 allows light emitted by the transmitter 5and transmitted by the transmitter fiber 3 to be injected into thetransmission fiber, optimally with the use of a further focusing lens22, in-plane or out-of-plane. Accordingly, in normal operation a firstoptical signal is withdrawn from the transmission fiber 2 and detectedby the receiver 6, and a second optical signal is injected into thetransmission fiber 2 from the transmitter 5. Preferably, in the state ofFIG. 1, the member 11 is resiliently urged in contact with the member 13using resilient springs 14.

In addition, attenuating means 16 optimally can be provided to reduce amagnitude of the first optical signal in the transmission optical fiberat a location downstream from the location where a portion of the firstoptical signal is withdrawn from the transmission fiber for detection bythe receiver 6 so as to improve a signal-to-noise ratio between thesignal being injected at the second location in the transmission opticalfiber from transmitter 5 and the original first optical signal beingpropagated by the transmission fiber and into the optical bypass switch.In the embodiment of FIGS. 1 and 2, the attenuating means comprises aseries of bends in the optical fiber. Other attenuating means are alsousable in accordance with the present invention, e.g. circular bends,etc.

In the normal state shown in FIG. 1, a second bending member 12 is shownin a disengaged state from a member 15. In this attitude, minimalbending of either the transmission optical fiber 3 or the receiveroptical fiber 4 is created by the members 12, 15. However, in the bypassstate shown in FIG. 2, the member 12 has been moved downward along thedirection of arrows 19 from the state illustrated in FIG. 1 so that thetransmitter optical fiber 3 is bent at location 31 an amount sufficientfor the second optical signal from the transmitter 5 to be withdrawnfrom the fiber 3 and "loop backed" and injected into a bend 32 in thereceiver optical fiber 4 thus allowing the receiver 6 to detect thesecond optical signal. According to the embodiment illustrated,connecting means for connecting the transmitter and receiver fibers soas to allow the second signal to be transmitted from the transmitter tothe receiver includes the bends, 31, 32, optimally focusing lenses 23,24, and preferably a connecting optical fiber 25 arranged asillustrated. Since the first and second bending members 11, 12 areinterconnected and moveable integrally, in the bypass state illustratedin FIG. 2, the member 11 is shown substantially disengaged from itsmating member 13 thereby substantially disengaging the means for bendingthe transmission optical fiber for signal withdrawal, injection, andattenuation. Thus in the bypass state a node connected to the opticalbypass switch is transparent to a network using the transmission opticalfiber so that signals being transmitted thereby can bypass that node. Inaddition, since in the bypass state the transmitter 5 is opticallyconnected to the receiver 6, by the use of logic means 28, the opticalbypass switch can easily determine whether or not the transmitter andreceiver are operating properly so that the optical bypass switch cansafely be returned to its normal state and adequately receive and detectthen first optical signals on the transmission optical fiber and thefurther inject second optical signals into the transmission opticalfiber, as desired.

FIG. 3 illustrates a sectional view of a drive mechanism for moving thefirst and second bending members 11, 12 between the states illustratedin FIGS. 1 and 2, e.g. the normal and bypass states. Referring to FIG.3, the bypass means drive includes a moveable permanent magnet 42connected to a similarly moveable primary ferromagnetic material 43. Thebypass means drive further includes first and second electromagnets 46,47 respectively connected to first and second ferromagnetic materials47, 48, these materials and electromagnets being stationary. Referencenumeral 49 illustrates an electrical current carrying coil foractivating the electromagnets 45, 46. In one state, e.g. the normalstate for the optical bypass switch, the primary ferromagnetic material43 is in contact with the first ferromagnetic material 47 due to astrength of the magnetic field created by the permanent magnet 42 whencurrent is not being conducted by the coil 49. When the optical bypassswitch is to enter its bypass state, a current is generated andtransmitted by the coil 49 in either or both of the electromagnets so asto create a force which either repels the permanent magnet 42 away fromthe first electromagnet 45 and/or alternatively attracts the permanentmagnet 42 towards the second electromagnet 46. Optimally, the coil 49can be arranged around the electromagnets such that when the bypassstate is desired, a field created by the first electromagnet 45 repelsthe field created by the permanent magnet 42 and the field created bythe second electromagnet 46 attracts the field generated by thepermanent magnet 42. Accordingly, the permanent magnet 42 is repelledfrom the first electromagnet 45 and first ferromagnetic material 47 andattracted towards the second electromagnet 46 and the secondferromagnetic material 48 so as to achieve the state illustrated in FIG.4. Once in this state, it is apparent that the current source can bediscontinued and further movement will not occur due to the normalattractive force normally created between the ferromagnetic materials43, 48 due to the magnetic field generated by the permanent magnet 42.Likewise, when the optical bypass switch is to return to its normalstate, a reverse current can be generated in the coil 49 thus repellingthe permanent magnet 42 from the second electromagnet 46 and towards thefirst electromagnet 45. According to a preferred embodiment, the firstand second electromagnets are respectively located in a vicinity of thebypass switch stationary members 13, 15, with the moveable first andsecond bending members 11, 12 being attached to the moveable permanentmagnet 42 so as to be moveable therewith. According to one preferredembodiment, two sets of drive magnets are used, one on each longitudinalend of the members 11, 12 so as to avoid or minimize any rotationaltorques imposed on the members 11, 12 which are selectively engageablewith either the stationary members 13, 15.

A further feature of the invention is illustrated in FIG. 5, this figureillustrating details of the members 11, 13 used to bend the transmissionoptical fiber. Specifically, the member 13 forms a curved channel 51having a curved end 52 against which an optical fiber is to beresiliently urged, the channel 51 including a top and bottom facerespectively which are optimally separated by a distance approximatelyequal to an outside diameter of an outer coating layer of thetransmission optical fiber to be bent. To reduce tolerance requirements,the top and bottom faces can be separated by a distance somewhat largerthan the outside diameter of the optical fiber outer coating layer, e.g.as much as twice this diameter, though optimally the distance is lessthan 1.5 this diameter, preferably between 1.5 and 1.0 times thisdiameter. The first bending member 11 has a thickness substantiallycorresponding to the separation distance between the top and bottomchannels 53, 54 of the stationary member 13 and has an end face profile55 corresponding to that of the curved end 52 of the stationary member13. Accordingly, in the bypass state of FIG. 2, the transmission opticalfiber can be loosely contained within the channel 51 and yet captivatedby the engaging end 55 of the first bending member 11, the curved end 52and top and bottom faces 53, 54 of the stationary member 13. When thebypass switch enters its normal state, the first bending member 11 isresiliently urged so that its end 55 is resiliently urged against theoptical fiber and against the channel end 52 thus creating the bends33-35 in the transmission optical fiber, as desired. A preferredembodiment of the construction of the means 31, 32 for bending thetransmission and receiver optical fibers is similar to that used for thebending means 33, 34, 35 with the addition of the provision of atransfer means 53 which allows each of the transmitter and receiverfibers to be selectively bent by only one of the means 31, 32.Specifically, referring to the transmitter optical fiber 4, in thebypass state it is captivated and bent between an end of member 12 and achannel end in the stationary member 15 in the manner described byreference to FIG. 5. However, after the bend 32, e.g. to the left inFIG. 2, the transmitter optical fiber travels vertically in the area 53and can be placed so as to normally reside outside the captivating areato be formed by the end of the member 12 and the stationary memberchannel for creating the bend 32. According to the embodimentillustrated, the transmitter optical fiber in this location is shownbeneath the channel.

An alternative embodiment is to locate the section of the fiber betweeneither the top or bottom face of the channel and a flat face of themember 19 extending substantially perpendicular to the end whichresiliently urges the receiver fiber into the bend 31. Similarly, thetransmitter optical fiber is bent at the location 31 in the mannerillustrated in FIG. 5 and then in the area 53 is moved vertically so asto be located in an area where it is not captivated between the member19 and the member 15 in an area that the bend 32. It will be appreciatedthat once the transmitter and receiver fibers are appropriately located,the members 11, 12 can be repetitively moved along the direction of thearrows illustrated in FIGS. 1 and 2 without the transmission andreceiver optical fibers being removed from their desired locations so asto be engageable with only one of the bending means 31, 32, one for eachfiber.

Though the invention has been described by reference to certainpreferred embodiments thereof, the invention is not to be limitedthereby and only by the appended claims.

We claim:
 1. An optical bypass switch, comprising:an optical receiver; an optical transmitter; means for withdrawing a first optical signal from a first bend in a transmission optical fiber at a first location and transmitting the first optical signal to the receiver; means for injecting a second optical signal from the transmitter into the transmission optical fiber at a second bend at a second location downstream of the first location on the transmission optical fiber; bypass means for disengaging the withdrawing means and the injecting means from the transmission fiber in a bypass state so that the first optical signal can be transmitted past the withdrawing and injecting means, the bypass means including connector means for connecting the transmitter with the receiver so that signals transmitted by the transmitter can be detected by the receiver in the bypass state.
 2. The bypass switch of claim 1, the connecting means including means for withdrawing the second optical signal from a transmitter optical fiber connected to the transmitter and means for injecting the second optical signal into a receiver optical fiber connected to the receiver.
 3. The bypass switch of claim 2, the connecting means including a connector optical fiber which has a first end which receives the second optical signal withdrawn from the transmitter optical fiber and a second end which transmits the second optical signal toward the receiver optical fiber.
 4. The bypass switch of claim 1, further comprising logic means for sensing an improper state of operation of at least one of the transmitter and receiver and connector means, the logic means maintaining the bypass means in the bypass state when the improper state is sensed.
 5. The bypass switch of claim 1, the bypass means including a moveable permanent magnet connected to a moveable primary ferromagnetic material, a first stationary electromagnet connected to a first ferromagnetic material, and a second stationary electromagnet connected to a second ferromagnetic material, the ferromagnetic materials being arranged such that the primary ferromagnetic material is moveable and connects to the first ferromagnetic material when the first electromagnet has been activated in its attraction mode, the primary ferromagnetic material being moveable and connectable to the second ferromagnetic material when the second electromagnet is activatable to its attraction mode.
 6. The bypass switch of claim 5, the bypass means including a member engageable with the transmission fiber in a first moveable state of the permanent magnet, the bypass means including a second member which bends first and second fibers connected to the transmitter and receiver in a second moveable state of the moveable magnet, the members being connected to and being moveable with the permanent magnet. 